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The influence of eccentric and concentric exercise on mRNA expression of skeletal muscle regulators in young women

THE INFLUENCE OF ECCENTRIC AND CONCENTRIC EXERCISE ON mRNA
EXPRESSION OF SKELETAL MUSCLE REGULATORS IN YOUNG WOMEN
by
Nicole Elizabeth Jensky
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOKINESIOLOGY)
May 2008
Copyright 2008 Nicole Elizabeth Jensky

We hypothesized that high intensity eccentric exercise (EE) and concentric exercise (CE) would differentially affect important regulators of skeletal muscle hypertrophy. We therefore sought to evaluate changes in myostatin, follistatin and MyoD mRNA gene expression using EE and CE as probes to better understand the mechanisms of muscle hypertrophy in young women. Twelve recreationally active women performed single-leg maximal eccentric [n=6, 25±1yr (mean±SD), 59±7kg] or concentric [n=6, 24±1 yr, 65±7kg] isokinetic exercise at 60°/s. Participants performed 10 sets of 10 maximal repetitions with 20 second rest between sets. Three muscle biopsies of the vastus lateralis were obtained from the exercised leg at baseline (biopsy #1), 8 hours after the first exercise bout (biopsy #2), and 8 hours after the seventh and final exercise bout performed 2 weeks after the first exercise session (biopsy #3). mRNA gene expression was determined using RT-PCR. For the CE group, there were no changes in myostatin, follistatin, and MyoD mRNA gene expression between biopsies #1 and #2, biopsy #1 and #3 (P equal to or greater than 0.07). For the EE group, there were no changes for the same variables (P equal to or greater than 0.17) except for MyoD expression which increased after one exercise bout (P=0.02). Differences between the EE and CE groups were not significant (P equal to or greater than 0.05). These data suggest that a single bout or multiple bouts of maximal EE or CE do not significantly alter myostatin or follistatin mRNA gene expression in young women. However MyoD mRNA expression appears to increase after EE. Therefore, the type of exercise stimulus may not differentially alter specific myogenic regulators.

THE INFLUENCE OF ECCENTRIC AND CONCENTRIC EXERCISE ON mRNA
EXPRESSION OF SKELETAL MUSCLE REGULATORS IN YOUNG WOMEN
by
Nicole Elizabeth Jensky
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOKINESIOLOGY)
May 2008
Copyright 2008 Nicole Elizabeth Jensky